Esters of γ-glutamyl amide of dopamine

ABSTRACT

Covers the esters of γ-glutamyl amide of dopamine selected from the group consisting of ##STR1## where R is a C 1  -C 18  alkyl radical, and a pharmaceutically acceptable acid addition salt thereof. Also covers the use of said esters of γ-glutamyl amide of dopamine to increase renal blood flow by administering said amide to warm-blooded mammals by clinically acceptable routes of administration such as oral, parenteral, rectal, etc.

This is a division of application Ser. No. 408,901 filed Oct. 23, 1973, now U.S. Pat. No. 3,910,988, issued Oct. 7, 1975.

BACKGROUND OF THE INVENTION

Dopamine has been reported to be useful in treating congestive heart failure and shock. In addition, certain amino acid amides of dopamine have been found useful as renal vasodilators and antihypertensive agents. (For example, see U.S. Pat. No. 3,676,492.) However, compounds disclosed in the just-mentioned patent and others which are used as renal vasodilators have the drawback that they also produce undesirable systemic hemodynamic changes.

It would be a distinct advance in the art if a compound could be discovered which has utility as a renal vasodilator but which does not also produce systemic hemodynamic changes such as increase in arterial blood pressure, heart rate, left ventricular systolic pressure, myocardial contractile force, etc.

SUMMARY OF THE INVENTION

We have now discovered compounds which are useful as renal vasodilators, and yet do not produce unwanted hemodynamic changes. In brief, these compounds are esters of γ-glutamyl amide of dopamine selected from the group consisting of ##STR2## where R is a C₁ -C₁₈ straight or branched chain alkyl radical, more preferably C₁ -C₆, and a pharmaceutically acceptable acid addition salt thereof. We have also discovered a method of increasing renal blood flow of warm-blooded animals by administering to said mammals at least an effective amount of the above renal vasodilator compound. Lastly, we have discovered that useful pharmaceutical compositions may be made using the dopamine amide as the active portion along with a pharmaceutically acceptable carrier.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the invention may be prepared by a wide variety of methods. The following examples illustrate typical procedures.

EXAMPLE I Preparation of N-CBZ-O⁵ -Succinimido-L-Glutamic Acid O-Ethyl Ester

To a solution of N-CBZ-L-glutamic acid-α-ethyl ester (0.096 mole, 29.6 g.) and N-hydroxysuccinimide (0.1 mole, 11.5 g.) in 200 ml. of dioxane was added with stirring at room temperature (0.1 mole, 21 g.) of dicyclohexylcarbodimide. After stirring 24 hours at room temperature, the mixture was filtered to remove dicyclohexylurea. The filtrate was concentrated in vacuo to give an oil. This oil failed to crystallize and was used in the next step without further purification.

EXAMPLE II Preparation of N-CBZ-[N⁵ -β-(3,4-Dibenzyloxyphenyl) Ethyl]-Glutamine O-Ethyl Ester

A solution of the active ester from above (˜0.1 mole) in 150 ml. dimethyl formamide was treated with dibenzyldopamine. HCl (0.1 mole, 37 g.) and triethylamine (0.2 mole, 28 ml.). This mixture was stirred at room temperature for four hours. The mixture was diluted with water to give an oil which on standing solidified to give a white solid. The solid was collected, washed with water and air dried. The moist solid was dissolved in boiling ethanol, filtered and allowed to crystallize. This white solid was collected to give 37.5 g. m.p. 115° - 8°. Recrystallized a second time from benzene to give 23 g. m.p. 126° - 8°. [α]_(D) ²³ = - 1.2 (C = 5, CHCl₃). Microanalysis for C₃₇ H₄₀ N₂ O₇ = 624.74 g./mole.

    ______________________________________                                                   Calc. %      Found %                                                 ______________________________________                                         C           71.14          71.11                                               H           6.45           6.53                                                N           4.48           4.57                                                ______________________________________                                    

EXAMPLE III Preparation of [N⁵ -α-(3,4-Dihydroxyphenyl) Ethyl]glutamine O-Ethyl Ester Hydrochloride

A suspension of the protected amide (0.37 mole, 23 g.) from above was reduced in a Parr apparatus in ethanol containing 5.0 g. 5% Pd.C and 1 eq. of concentrated HCl. After uptake was complete, the catalyst was filtered and washed with ethanol. The filtrate was concentrated in vacuo to give, upon repeated azeotroping with ethanol, a glass. This glass was dried under high vacuum at 60° for 24 hours to give 11.4 g. (89%) of a hygroscopic glass. [α]_(D) ²³ = +11.0 (C = 2, H₂ O). Microanalysis for C₁₅ H₂₃ ClN 2O₅ = 346.81 g./mole.

    ______________________________________                                         Calc. % (1% H.sub.2 O) Found %                                                 ______________________________________                                         C           51.44          51.30                                               H           6.75           6.67                                                N           8.00           7.77                                                ______________________________________                                    

EXAMPLE IV Preparation of N-CBZ-O⁵ -Succinimido-L-Glutamic Acid O-Methyl Ester

This ester was prepared in the same manner as was the ethyl ester. The oil obtained was used in the next step without further purification.

EXAMPLE V Preparation of N-CBZ-[N⁵ -β-(3,4-Dibenzyloxyphenyl) Ethyl]-Glutamine O-Methyl Ester

The crude oil from above was used to prepare the protected dopamine amide in the same way for the ethyl ester. The crude product was recrystallized twice from MeOH:Water (5:1) to give a white crystalline solid, m.p. 75° - 80°. Yield was 10.0 g. [α]_(D) ²³ = -3.0 (C = 5CHCl₃).

EXAMPLE VI Preparation of [N⁵ -β-(3,4-Dihydroxyphenyl)Ethyl]-Glutamine O-Methyl Ester Hydrochloride

The protected amide from above (0.016 mole, 10 g.) was reduced in the same manner as for the ethyl ester. Yield of hygroscopic glass was 3.0 g. [α]_(D) ²³ = +9.94 (C =5, H₂ O). Microanalysis for C₁₄ H₂₁ ClN₂ O₅ = 332.79 g./mole.

    ______________________________________                                         Calc. % (2% H.sub.2 O) Found %                                                 ______________________________________                                         C           49.54          49.44                                               H           6.43           6.46                                                N           8.25           8.36                                                ______________________________________                                    

EXAMPLES VII - X

Similarly were prepared [N⁵ -β-(3,4-dihydroxyphenyl) ethyl]-glutamine O-isopropyl ester hydrochloride, [N⁵ -β-(3,4-dihydroxyphenyl)ethyl]-glutamine O-t-butyl ester hydrochloride, [N⁵ -β-(3,4-dihydroxyphenyl)ethyl]-glutamine O-isobutyl ester hydrochloride, and [N⁵ -β-(3,4-dihydroxyphenyl)ethyl]-glutamine O-stearyl ester hydrochloride.

The compounds of this invention are renal vasodilators and have been found to significantly increase renal blood flow in test animals. The compounds are useful as specific renal vasodilators which may be useful as antihypertensive agents, diuretics, agents used to treat shock and congestive heart failure and compounds used to treat edema and to detoxify poisons such as barbituates.

Anesthetized dogs were tested to measure the increase in renal arterial blood flow after being administered with a compound of the invention. With regard to the anesthetized dogs, the following test procedure was employed:

Dogs of either sex, weighing between 9 and 15 kg. were anesthetized with barbital sodium (250 mg./kg. intravenously) following sedation with morphine sulfate (3 mg./kg. subcutaneously), 30 minutes earlier. A polyethylene catheter was placed in the abdominal aorta via the femoral artery to monitor the aortic blood pressure. Another polyethylene cannula was advanced into the left ventricular cavity via the left carotid artery to record left ventricular peak systolic pressure (LVSP). Heart rate was counted from lead II electrocardiogram. A precalibrated electromagnetic flow probe (Carolina Medical Electronics) and an occluding cuff were positioned around the right renal artery through a retroperitoneal approach. Zero blood flow was obtained by inflating the occluding cuff for a short period (10 - 30 seconds). Aortic blood pressure, left ventricular pressure, heart rate and renal blood flows were recorded continuously on a Grass Model 7 Polygraph.

In anesthetized dogs, dopamine and the compounds of Examples III and VI were compared after intravenous and intraduodenal injections. Whereas the renal vasodilator action of dopamine was accompanied by pronounced increase in arterial blood pressure, heart rate, left ventricular systolic pressure and dp/dt, greater increases in renal blood flow after treatment with the subject esters of γ-glutamyl amide of dopamine were obtained without such changes. In fact, with the dose of 45 mg./kg. of dopamine, one observes hemodynamic changes which overcome its renal vasodilator action, whereas equimolar doses of the subject esters of γ-glutamyl amide of dopamine increase renal blood flow to values not achievable with dopamine alone. Thus, as can be seen from Table I below, there is a clear disassociation between the renal vasodilator action and systemic hemodynamic effects for the compounds of Examples III and VI, but not for dopamine.

                                      Table I                                      __________________________________________________________________________     Effect on Renal Blood Flow in Anesthetized Dogs by Intraduodenal Route of      Administration                                                                               Peak Effect                                                                            Total Effect  Time for Peak                              Compound,                                                                            Control Flow                                                                           Change          Change                                                                               Effect   Duration                          Dose  (ml/min)                                                                               (%)     (ml)    (%)   (min)    (min)                             __________________________________________________________________________     Example                                                                        VI                                                                             78 mg/kg                                                                             107     58.9    6225.50 23.84 27       244                               Example                                                                        III                                                                            81 mg/kg                                                                             115     56.5    12694.00                                                                               34.38 195      321                               Dopamine                                                                             107     *23.4   408.5   15.27  7       25                                45 mg/kg      -41.2   -3789.  -19.67                                                                               71       >180                              Systemic Hemodynamic Effects                                                          Mean Aortic Blood     Left Ventricular                                                                            Estimated                                   Pressure     Heart Rate                                                                              Systolic Pressure                                                                           Max dp/dt                            Compound,                                                                             Change       Change   Change       Change                               Dose   (%)          (%)      (%)          (%)                                  __________________________________________________________________________     Example                                                                        VI                                                                             78 mg/kg                                                                              -10.9        -24.3    -9.2         28.4                                 Example                                                                        III                                                                            81 mg/kg                                                                              23.0         -16.4    26.7         72.7                                 Dopamine                                                                              50.4         *-10.4   76.1         208.3                                45 mg/kg            +38.4                                                      __________________________________________________________________________      *Dopamine produced a biphasic change in renal blood flow and heart rate:       An initial increase of short duration followed by a marked and sustained       decrease in renal blood flow.                                            

In summary then, it has been found that [N⁵ -β-(3,4-dihydroxyphenyl)-ethyl]-glutamine esters or ester hydrochlorides are highly unusual selective renal vasodilators. After administering the compounds, one notes the following unusual properties: marked increase in renal blood flow, prolonged duration of action, minimal systemic hemodynamic actions even in extremely large doses, and maintenance of activity even after intraduodenal administration.

The compounds of the invention can be administered in dosages of from about 0.01 mg./kg. up to about 2500 mg./kg. dependent upon the route of administration, either single dose or by infusion.

While the compounds can be administered as a free base, it is generally preferred to employ the compounds as their pharmaceutically acceptable acid addition salts. Such salts are easily prepared by methods known to the art. The base is reacted with either the calculated amount of an organic or inorganic acid in an aqueous miscible solvent, such as acetone or ethanol, with isolation of the salt by concentration and cooling, or with an excess of the acid in an aqueous immiscible solvent, such as ethyl ether or chloroform, with the desired salt separating directly. Exemplary of such organic salts are those made with such acids as maleic, fumaric, benzoic, ascorbic, pamoic, succinic, bismethylenesalicylic, methylsulfonic, ethanesulfonic, acetic, propionic, tartaric, salicylic, citric, gluconic, lactic, malic, mandelic, innamic, citraconic, aspartic, stearic, palmitic, itaconic, glycolic, p-aminobenzoic, glutamic, benzene sulfonic, cyclohexylsulfamic, and theophylline acetic acids as well as with the 8-halotheophyllines, for example, 8-chlorotheophylline and 8-bromotheophylline. Exemplary of such inorganic salts are those with hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric and nitric acids. Of course, these salts may also be prepared by the classical method of double decomposition of appropriate salts which is well known to the art. Also included within the purview of this invention are the nontoxic quaternary ammonium salts which include those formed with alkyl halides (e.g., methyl chloride, isobutyl bromide, dodecyl chloride and cetyl iodide), benzyl halides (e.g., benzyl chloride) and dilower alkyl sulfates (e.g., dimethyl sulfate).

The compounds useful in the practice of the present invention are generally formulated into pharmaceutical compositions comprising, as an active ingredient, at least one of the active agents in association with a pharmaceutical carrier or diluent. The compounds useful in the practice of the invention exhibit both oral and parenteral activity and can be formulated in dosage forms for oral or parenteral administration.

Solid dosage forms for oral administration include capsules, tablets, pills, powders and granules. In such solid dosage forms, the active compound is admixed with at least one inert diluent such as sucrose, lactose or starch. Such dosage forms can also comprise, as is normal practice, additional substances other than inert diluents, e.g., lubricating agents such as magnesium stearate, sweetening and flavoring agents, and the like. In the case of capsules, for example, the active agent may be the sole ingredient.

Liquid dosage forms for oral administration include pharmaceutically acceptable emulsions, solutions, suspensions, syrups, and elixirs containing inert diluents commonly used in the art, such as water. Besides inert diluents, such compositions can also include adjuvants, such as wetting agents, emulsifying and suspending agents, and sweetening, flavoring and perfuming agents.

Preparations according to this invention for parenteral administration include sterile aqueous or nonaqueous solutions, suspensions or emulsions. Examples of nonaqueous solvents or vehicles are propylene glycol, polyethylene glycol, vegetable oils, such as olive oil and injectable organic esters such as ethyl oleate. Such dosage forms may also contain adjuvants such as preserving, wetting, emulsifying and dispersing agents. They may be sterilized by, for example, filtration through a bacteria-retaining filter, by incorporating sterilizing agents into the compositions, by irradiating the compositions, or by heating the compositions. They can also be manufactured in the form of sterile solid compositions which can be dissolved in sterile water, or some other sterile injectable medium immediately before use.

The dosage of active ingredient in the composition of this invention may be varied; however, it is necessary that the amount of the active ingredient shall be such that a suitable dosage form is obtained. The selected dosage depends upon the desired therapeutic effect, on the route of administration, and on the duration of the treatment.

The following further illustrates pharmaceutical compositions in oral dosage form:

In order to prepare capsules, the following procedure was employed: Specifically, here sufficient pharmaceutical composition was formulated to prepare 1000 capsules. 25.00 Gm. of [N⁵ -β-(3,4-dihydroxyphenyl)-ethyl]-glutamine hydrochloride ester was preblended with 212.5 gm. of lactose, U.S.P. and 12.5 gm. of talc, U.S.P. The preblend was then passed through a suitable screen and the screened powders were then blended. The powders were then filtered into gelatin size No. 3 capsules. The filled weight of ten capsules was 2.50 gm. The filled capsules were then cleaned with sodium chloride.

The following formulation is a typical tablet formula which may be used to incorporate the compound:

                  Table II                                                         ______________________________________                                           Ingredient          Amount/Tablet                                            ______________________________________                                         Starch U.S.P. Corn    13 mg.                                                   [N.sup.5 -β-(3,4-dihydroxyphenyl)-                                         ethyl]-glutamine hydrochloride                                                 ester                50 mg.                                                   Calcium Phosphate Dibasic NF                                                    Dihydrate            132 mg.                                                  Water Purified U.S.P. Distilled                                                                      q.s.                                                     Magnesium Stearate     1 mg.                                                   Talcum (Talc U.S.P.) Powder                                                                           4 mg.                                                                         200 mg.                                                  ______________________________________                                    

Tablets are prepared by using the above formula as follows: First a granulating step is carried out. Here a starch paste is made by adding 8 mg. of cornstarch to water and then heating. The compound is then milled with 5 mg. of additional cornstarch in an equal volume of calcium phosphate dibasic through a 40 mesh screen into a mass mixer. After sufficient mixing the balance of the calcium phosphate dibasic is milled through the 40 mesh screen and thereafter added to the mixer.

The hot cornstarch paste is then also added to the mixer and mixing is carried out until a granular stage is reached. In some instances additional warm water may be added, if necessary. Granulation is carried out through a 5/8 inch band. The granulated mixture is dried in a hot air oven at 50° C. overnight to 1.0% L.O.D. (Brabender 1/2 hr.). After drying the mixture is sifted and then ground to 16 mesh.

Lubricating is carried out by charging half of the granulation into a blender. Talc and magnesium stearate are screened through a 30 mesh screen and charged into the blender. The remainder of the granulation is added and blended 15 minutes.

In order to form tablets compression of the granulated material is carried out by using a 9/32 inch standard convex punch. The resultant tablets have a hardness of 7 - 9 and 10 tablets weigh 2.00 g. 

We claim:
 1. A method of increasing renal blood flow of warm-blooded mammals which comprises administering to said mammals at least an effective amount of a renal vasodilator compound of the formula ##STR3##where R is a straight or branched chain alkyl containing 1 to 18 carbon atoms and a pharmaceutically acceptable acid addition salt thereof.
 2. The method of claim 1 wherein said salt is a hydrochloride salt.
 3. A pharmaceutical composition in unit dosage comprising an effective amount of a renal vasodilator compounds of the formula ##STR4##where R is a straight or branched chain alkyl containing 1 to 18 carbon atoms and a pharmaceutically acceptable acid addition salt thereof; and a pharmaceutically acceptable carrier.
 4. The composition of claim 3 wherein said ester is a hydrochloride salt. 